The subject invention relates generally to pipe insulation products and more specifically to pipe insulation products comprising a vapor-barrier stop.
Piping is often used to transport one or more fluids between destinations. For example, piping may be used to transport water, petroleum, oxygen, etc. The piping is often made from a metal material, such as copper, stainless steel, galvanized steel, aluminum, brass, titanium, etc., or from a plastic material, such as polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), fiber reinforced plastic (FRP), polypropylene (PP), polyethylene (PE), etc. Piping may also be made from a ceramic, fiberglass, or concrete material, although these pipes are less common.
During fluid transportation, the fluid may be subject to heating and/or cooling from the surrounding environment. For example, the fluid may be transported in either a hot or cold state relative to the surrounding environment, which induces heat transfer to or from the fluid and pipes. HVAC systems are a common example of systems that routinely utilize various pipe configurations to transport hot or cold fluids. Due to the conductive nature of the pipes (especially metal pipes), heat may be conducted to or from the fluid during transportation. The addition or removal of heat may result in the decreased efficiency of a system and/or increased time and/or expense in operating the system. For example, in HVAC systems, the addition of heat to cooled fluids may result in loss of efficiency for a cooling unit and may also result in increased expense because of increased operating time and energy needed to achieve a desired cooling level.
In some cases, the fluid being transported is a compressed liquefied gas or a cryogenic liquid. Exemplary liquefied gases where the present technology may be useful include liquefied natural gas, liquefied ethylene, liquefied ammonia, or other fluids in their respective liquid states. For example, the present technology may be useful for transporting liquefied natural gas at about −260° F., liquefied ethylene at about −155° F., liquefied ammonia at about −28° F., etc. A cryogenic liquid is a liquid with a normal boiling point below approximately −130° F. (−90° C.). This means that at ambient conditions, the cryogenic liquid would be in a gaseous state. Generally, the otherwise gaseous fluid is compressed and chilled into a liquid state for transportation purposes.
To reduce heat transfer during fluid transportation, pipe insulation products are commonly installed on the pipes of a piping system to retard the flow of heat to and from the pipes. Commonly, one or more sections of pipe are fitted with a pipe insulation product where the sections of pipe are generally fully encased within the pipe insulation product. Common pipe insulation products comprise a fibrous insulation material that is surrounded by and encased within a laminate. Separate sections of pipe insulation product are often coupled together via adhesive tapes. The laminates of the pipe insulation product often enhance the visual appeal of the piping system and serve as a means for sealing the pipe insulation product about the pipes of the piping system. Individual segments of pipe insulation products typically range in length from about 36 inches to about 48 inches; have a wall thickness ranging from about 0.5 inches to about 3 inches; and a range in outside diameter from about 2 inches to about 32 inches. The pipe insulation product may also be used to reduce degradation and/or corrosion of the pipe.
For cryogenic piping systems, commonly referred to as cryogenic trains, insulating the sections of pipe is necessary due to the extremely low temperatures of the cryogenic liquid required to be maintained during transportation. However, insulating cryogenic trains can be challenging due to the particular characteristics of cryogenic liquids. Not only are cryogenic liquids difficult to transport because of their extremely low temperatures (often −100° F. to −260° F., or −73° C. to −162° C.), but many cryogenic liquids are also flammable or combustible. For example, commonly transported cryogenic liquids include methane, liquefied natural gas (LNG), and oxygen.
A primary challenge of insulating cryogenic trains is the extreme temperature differential between the cryogenic liquid being transported and the ambient air. A higher temperature differential results in a higher rate of heat loss. A high rate of heat loss is likely to result in higher inefficiencies of the overall system and may increase the risk of vaporization. Without adequate insulation, the cryogenic liquid is at risk of heating up and vaporizing as a result of the temperature increase. The volume of a cryogenic liquid, for example liquefied natural gas (LNG) can be up to 1/600th of the volume of the natural gas in the gaseous state. Thus, vaporization of the cryogenic fluid back to its gaseous state while still inside of the pipe is likely to result in damage to the piping system, and may result in damage to any upstream or downstream equipment connected to the piping system.
Insulation systems for below-ambient conditions must be designed to be vapor tight. This is particularly true for insulation systems that are designed for use in cryogenic operating temperatures. Water intrusion into the system may degrade the performance of the insulation system and can lead to other problems. For example, condensation is likely to form on any exposed pipe because of the extreme temperature differential between the cryogenic liquid and ambient air. Ambient air will condense on surfaces that are below the dew point of the ambient air. Since cryogenic trains operate well below the ambient air dew point, condensation is a common problem. Condensation is problematic because it can adversely impact the quality of the piping material, in some cases causing corrosion. Additionally, condensation is likely to damage the insulation segments jacketing the pipe. Once a section of insulation comes into contact with condensation, the condensation is likely to move laterally down the insulation segment, expanding the overall range of damage to the insulation system.
Moisture intrusion can also lead to ice formation within the insulation system and/or ice formation on the pipe itself. Ice formation within the insulation system is likely to reduce the system efficiency and degrade the insulation system performance. Ice formation also adds unwanted weight to the piping system that can lead to equipment damage if the weight exceeds the load capacities of the supports or equipment.
Leaks in the vapor barrier of the insulation are another source of moisture intrusion common for insulation systems. It is likely that a vapor barrier system is going to leak at some point in its lifetime. The leak can be a pinhole or larger rupture that permits moisture vapor into the closed system that will be absorbed by the insulation segments, condense as water in the voids between joints and layers, freeze and expand and lead to degradation of the insulation system's performance. Again, once the leak is absorbed by the insulation system, it is likely to move laterally as vapor or liquid down the pipe, extending the range of damage to the insulation system.
Piping interruptions are a primary source of moisture intrusion risk for a piping system. All insulation systems, including cryogenic trains, have piping interruptions. A piping interruption is any break or component that breaks an otherwise straight run of piping. Common piping interruptions include piping elbows or tees, valves, flanges, piping termination points, piping supports, and inline instruments. Even if the piping run is straight without interruption, if the piping run is 18 or more feet long, a contraction joint is typically required. A contraction joint is also a type of piping interruption. This means, that for almost all piping systems, a piping interruption occurs every 18 feet or less on a pipe.
Vapor-barrier stops are applied to insulation segments at piping interruption points to isolate the insulation segment at piping interruptions to ensure any break in the insulation system or damage to the insulation system does not allow for lateral movement of any vapor or fluid down the pipe, which may compromise the entire insulation system. Vapor-barrier stops are applied to the pipe and overlap the insulation. Commonly, vapor-barrier stops are constructed using adhesives and sealants imbedded with a fabric scrim to reinforce the stop. The vapor-barrier stops are commonly adhered to and integrated with any vapor barrier jacket to maintain a continuous vapor barrier system. Additional vapor control layers and protective metal jacket are then, generally, applied over the insulated piping with vapor-barrier stops.
In cryogenic situations, such as liquefied natural gas, gas is gathered, compressed into a liquid form and sent out to a storage tank. From the storage tank the liquefied gas is then pumped out to a ship for exportation. Often a single train is at least a mile long. Since insulating the entire train is necessary due to the temperature requirements of cryogenic systems, vapor-barrier stops are required at least every 18 feet along the entirety of the train.
Generally, every year approximately 5% or more of sub-ambient piping systems insulation will need to be replaced due to condensation, leaks, or other damage to the insulation system. By employing vapor-barrier stops, the damage to the insulation system is limited to the segment of insulation between the two vapor-barrier stops. Instead of allowing a leak or condensation to travel down the entirety of a piping section, which can be up to a mile long, the damage is contained to a length of insulation between vapor barrier stops of approximately 18 feet or less.
On a typical job site, when an piping interruption is encountered, a vapor-barrier stop is applied. Often times piping interruptions are located in hard to reach areas. Thus, to apply a vapor-barrier stop in the field, scaffolding, or other equipment, is often required simply to reach the piping interruption. Additionally, the geographical location of facilities that the piping systems are connected to tend to be in isolated regions, often areas where extreme weather conditions are common. For example, many LNG facilities are located in coastal areas such as southern Texas along the Gulf of Mexico. Thus, workers installing vapor-barrier stops at the job sites are often exposed to high humidity and hot conditions during installation.
Skilled labor is generally required to apply vapor-barrier stops in the field. Facilities often encounter issues of limited workers available who have the skills necessary to install vapor-barrier stops on-site. Of the workers that a facility is able to find, many of these workers do not have the required skills or experience to adequately apply the vapor-barrier stops. This lends to issues of botched or misapplied vapor-barrier stops.